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Flux pumps provide a contact-free method of energizing dc currents in superconducting coils. Since a predictive quantitative theory for dynamo-type flux pumps does not exist yet, the optimization of device designs must proceed through empirical experiment. In this paper, we investigate the effect of varying the annularwidth of the iron stator yokewithin a high-temperature superconducting dynamo. Reducing the dimensions of this iron yoke reduces the mass of cold iron within the dynamo, and hence has advantages in terms of weight, cryogenic efficiency, and eddy current losses. In this paper, we have investigated the dc output from an experimental high-temperature superconductor (HTS) dynamo in which the annular width of the iron yoke Δr is varied across a factor of four. Varying this dimension affects the reluctance of the magnetic circuit formed between the rotor and stator. We have shown that the dynamo output is surprisingly insensitive to the size of the iron yoke. The maximum current output (Isc ) is independent of Δr at all flux gaps. At the closest magnet-stator flux gap, a fourfold increase in Δr results in only a ~30% increase in the open circuit voltage (Voc ) and internal resistance (Rd) of the dynamo. Our results indicate that the smallest yoke studied (Δr = 6 mm) can be utilized with a 25.4-mm Nd-Fe-B rotor magnet, without adverse impact on the electrical performance of this type of HTS dynamo. [ABSTRACT FROM AUTHOR]

In this paper, a new linear Vernier permanent-magnet machine is proposed. By using high-temperature superconducting (HTS) winding to provide an additional field excitation, a hybrid excitation machine is achieved. The HTS field winding is accommodated in the stator and PMs are mounted on the mover surface. By regulating the dc current flowing in the HTS field winding, the air-gap flux can be flexibly controlled. First, the proposed machine and the cooling system for the HTS field winding are presented. Second, the operating principle of the proposed machine is discussed. Third, by using the 3-D finite element method, the performance of the proposed machine is evaluated. Finally, a conclusion is drawn. [ABSTRACT FROM PUBLISHER]

In a High Temperature Superconducting (HTS) magnet consisting of pancake windings, HTS tape with the same width has been used for all pancake windings. If a wider HTS tape is used for the outer pancake windings, the critical current of the HTS magnet can be increased. This paper shows the properties of BSCCO magnets in which the outer pancake windings are wound with a wider HTS tape. In order to examine the effects of a wider HTS tape, a HTS magnet with an inner radius of 20 mm and a height of 202.4 mm was used. The number of turns of each pancake winding was 150, and the number of pancake windings was 46. The critical current of the pancake winding was determined by using E-J relation. Results of calculation show that the critical current was higher in the HTS magnet with a wider HTS tape at the outer pancake windings than in the HTS magnet with the same width of HTS tape for all pancake windings. [ABSTRACT FROM PUBLISHER]

General Electric, under contract with the Air Force Research Labs (AFRL), has successfully developed and tested a high speed, multimegawatt superconducting generator. The generator was built to demonstrate high temperature superconducting (HTS) generator technology for application in a high power density Multimegawatt Electric Power System (MEPS) for the Air Force. The demonstration tested the generator under load conditions up to 1.3 MW at over 10,000 rpm. The new MEPS generator achieved 97% efficiency including cryocooler losses. All test results indicate that the generator has a significant margin over the test points and that its performance is consistent with program specifications. This demonstration is the first successful full-load test of a superconducting generator for the Air Force. In this paper we describe the development of the generator and present some key test results used to validate the design. Extrapolation to a higher power density generator is also discussed. [ABSTRACT FROM AUTHOR]

This paper describes design and operation of a three-phase HTS power transformer with capacity of 630 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 10.5 kV/0.4 kV. The windings were wound by hermetic stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. Cryostat is made from electrical insulating materials with room temperature bore for commercial amorphous alloy core. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The ac losses were calculated and measured by method of conventional transformer. The HTS power transformer successfully operated in a live power grid. [ABSTRACT FROM AUTHOR]

This paper presents design and test of a single-phase HTS transformer with capacity of 45 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 2400/160 V. The windings were wound by stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. The gas-cooling current leads of secondary windings were chosen in order to reduce heat input. Cryostat is made from electrical insulating materials with room temperature bore for iron core made of the commercial Fe-Si steel. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The AC losses were calculated and measured by calorimetric method with a mass flow meter of nitrogen gas at room temperature. The performances of the transformer in accidental cases of sudden short-circuit and lightning impulse were also tested. [ABSTRACT FROM AUTHOR]